Hereinafter, a term “nanoneedle” includes what terms “nanotube” and “nanowire” refer to.
An SPM is a device used in a field of nanoscale technology, which is very powerful and useful as well as being delicate. The SPM is distinguished into various kinds such as an atomic force microscope (AFM) utilizing an atomic force applied between a probe and a sample object, a magnetic force microscope (MFM) utilizing a magnetic force applied between the probe and the sample object, an electrostatic force microscope (EFM) utilizing an electrostatic force applied between the probe and the sample object, and a scanning near field optical microscope (SNOM) utilizing an optical property of the sample object, etc.
Although it is widely known that the SPM as such has a resolution in atomic level, there still exists a need to sharpen an end (or a tip) of the probe used in the SPM to enhance the resolution of the SPM better. Because a conventional method which enhances an aspect ratio of a probe using semiconductor micromachining techniques has an inherent limitation in improving the resolution, a demand for an alternative method has been increased for sharpening the end of the probe. As a result, a method using the carbon nanotube emerged as the new alternative.
The carbon nanotube has a high aspect ratio as well as excellent electrical and mechanical properties as well known. Accordingly, a research has been undertaken on a method for scanning a sample object by the carbon nanotube attached on the tip of the SPM probe (mother probe).
As technologies related to the research mentioned above, there exist U.S. Pat. No. 6,528,785 which discloses a technology of attaching the carbon nanotube on the tip of the SPM probe using a coating film, and U.S. Pat. No. 6,759,653 which discloses a technology of attaching the carbon nanotube on the tip of the SPM probe using focused ion beam and severing the carbon nanotube attached on the tip of the SPM probe in a required length.
However, there are several significant technical factors in using the nanoneedle being attached on the tip of the SPM probe in accordance with the series of those technologies. Those factors are as follows: First, the attaching strength of the nanoneedle on the tip of the SPM probe; Second, the length adjustment of the nanoneedle attached on the tip of the SPM probe; third, adjustment of a pointing direction and shape of the nanoneedle attached on the tip of the SPM probe regardless of shape of the tip of the SPM probe.
U.S. Pat. Nos. 6,528,785 and 6,759,653 mentioned above have successfully satisfied two factors out of those three technical factors mentioned above, which are the attaching strength and the length adjustment. However, the third factor remains unsolved by any of the methods disclosed so far.
Korean patent application number 10-2002-0052591 filed by the applicant of the present invention discloses a fabricating apparatus to adjust the pointing direction of the nanoneedle attached on the tip of the SPM probe and a method for fabricating such nanoneedle. However, Korean patent application 10-2002-0052591 still has technical disadvantages of long process time and high cost required to fabricate a nanoneedle SPM probe as well as low throughput because the patent application utilizes a nanomanipulator and a medium attached the tip of the probe to adjust the pointing direction of the nanoneedle.
Further, despite that the variation of the pointing direction of the nanoneedle attached on the tip of the SPM probe has to be within 2 to 3 degree to scan in critical dimension (CD), it is nearly impossible to correctly adjust the pointing direction of the nanoneedle with such an accuracy by the conventional technologies. In addition, it should be noted that adjusting the accuracy of the pointing direction of the nanoneedle is required not only for scanning in CD as described above, but also for obtaining a correct scanning image using a general nanoneedle SPM probe Particularly, in case where the nanoneedle attached on the tip of the probe, is long, it becomes a more important to adjust the accuracy of the pointing direction of the nanoneedle.
Besides, in some cases, the nanoneedle attached on the tip of the SPM probe is either crooked or curled due to certain manufacturing problems. Accordingly, a technical means is required to straighten the nanoneedle attached on the tip of the SPM probe for such cases.
Also, the conventional SPM probe or the SPM nanoneedle probe having an end with a shape of a straight line has a limitation in scanning the shape of the sidewall of the sample object having irregularity in nanoscale level. In other words, in case of scanning the sidewall of the sample object having irregularity in nanoscale level using the probe as shown in FIG. 12, a distorted image being different from the actual shape of the sidewall of the sample object is obtained instead as shown in FIG. 14 because the probe scans the sidewall illustrated in FIG. 13.
Although U.S. Pat. No. 6,246,054 disclosed the SPM probe having an end with shapes illustrated in FIG. 15, it still has a disadvantage in that the method to fabricate such probes and the scanning method are too complicated. Besides, it has a certain limitation in accuracy of the scanning the sidewall of a sample object to be scanned.
Due to problems mentioned above, an alternative is needed to solve the technical problems related to the SPM nanoneedle probe.